Hybrid light source

Abstract

A hybrid light source comprises a discrete-spectrum lamp (for example, a fluorescent lamp) and a continuous-spectrum lamp (for example, a halogen lamp). A control circuit individually controls the amount of power delivered to the discrete-spectrum lamp and the continuous-spectrum lamp in response to a phase-controlled voltage generated by a connected dimmer switch, such that a total light output of the hybrid light source ranges throughout a dimming range. The continuous-spectrum lamp is driven by a continuous-spectrum lamp drive circuit, which is operable to conduct a charging current of a power supply of the dimmer switch and to provide a path for enough current to flow through the hybrid light source, such that the magnitude of the current exceeds rated latching and holding currents of a thyristor of the dimmer.

1. A dimmable hybrid light source adapted to receive a phase-controlled voltage, the hybrid light source comprising:
 a discrete-spectrum light source circuit comprising a discrete-spectrum lamp; 
 a continuous-spectrum light source circuit comprising a continuous-spectrum lamp operable to conduct a continuous-spectrum lamp current; 
 a zero-crossing detect circuit for detecting when the magnitude of the phase-controlled voltage becomes greater than a predetermined zero-crossing threshold voltage each half-cycle of the phase-controlled voltage; and 
 a control circuit coupled to both the discrete-spectrum light source circuit and the continuous-spectrum light source circuit for individually controlling the amount of power delivered to each of the discrete-spectrum lamp and the continuous-spectrum lamp in response to the zero-crossing detect circuit, such that a total light output of the hybrid light source ranges from a minimum total intensity to a maximum total intensity, the control circuit operable to control the discrete-spectrum lamp when the total light intensity is below a transition intensity, such that the percentage of the total light intensity produced by the continuous-spectrum lamp is greater than the percentage of the total light intensity produced by the discrete-spectrum lamp when the total light intensity is below the transition intensity; 
 wherein the control circuit controls the amount of power delivered to the continuous-spectrum lamp to be greater than or equal to a minimum power level after the magnitude of the phase-controlled voltage becomes greater than the predetermined zero-crossing threshold voltage each half-cycle of the phase-controlled voltage when the total light intensity is above the transition intensity. 
 
     
     
       2. The hybrid light source of  claim 1 , wherein the continuous-spectrum light source circuit comprises at least one semiconductor switch coupled so as to control the flow of the continuous-spectrum lamp current through the continuous-spectrum lamp. 
     
     
       3. The hybrid light source of  claim 2 , wherein the control circuit controls the continuous-spectrum light source circuit to drive the semiconductor switch to be conductive and non-conductive with a duty cycle, the control circuit adjusting the duty cycle of the continuous-spectrum light source circuit to a minimum duty cycle such that the continuous-spectrum lamp conducts the continuous-spectrum lamp current after the magnitude of the phase-controlled voltage becomes greater than the predetermined zero-crossing threshold voltage each half-cycle of the phase-controlled voltage. 
     
     
       4. The hybrid light source of  claim 3 , wherein the control circuit adjusts the duty cycle of the continuous-spectrum light source circuit to a second duty cycle greater than the minimum duty cycle such that the continuous-spectrum lamp conducts the continuous-spectrum lamp current before the magnitude of the phase-controlled voltage becomes greater than the predetermined zero-crossing threshold voltage each half-cycle of the phase-controlled voltage. 
     
     
       5. The hybrid light source of  claim 4 , wherein the control circuit adjusts the duty cycle of the continuous-spectrum light source circuit to from the second duty cycle to the minimum duty cycle across a period of time when the zero-crossing detect circuit detects that the magnitude of the phase-controlled voltage has become greater than the predetermined zero-crossing threshold voltage. 
     
     
       6. The hybrid light source of  claim 3 , wherein the continuous-spectrum lamp comprises a low-voltage halogen lamp and the continuous-spectrum light source drive circuit comprises a low-voltage halogen drive circuit and a low-voltage transformer. 
     
     
       7. The hybrid light source of  claim 2 , further comprising:
 two input terminals adapted to receive the phase-controlled voltage; 
 a voltage doubler circuit coupled between the input terminals and generating a bus voltage at an output, the discrete-spectrum light source circuit coupled to the output of the voltage doubler circuit for receiving the bus voltage. 
 
     
     
       8. The hybrid light source of  claim 7 , wherein the discrete-spectrum lamp comprises a fluorescent lamp and the discrete-spectrum light source drive circuit comprises a ballast circuit for driving the fluorescent lamp, the ballast circuit comprising an inverter circuit for converting the bus voltage to a high-frequency AC voltage, and a resonant tank circuit for coupling the high-frequency AC voltage to the fluorescent lamp, the control circuit coupled to the inverter circuit for controlling the magnitude of a lamp current conducted through the fluorescent lamp. 
     
     
       9. The hybrid light source of  claim 7 , further comprising:
 a rectifier circuit coupled between the input terminals and generating a rectified voltage at an output, the series combination of the semiconductor switch and the continuous-spectrum lamp of the continuous-spectrum light source circuit coupled across the output of the rectifier circuit for receiving the second rectified voltage. 
 
     
     
       10. The hybrid light source of  claim 1 , wherein the continuous-spectrum light source circuit comprises a semiconductor switch coupled in series electrical connection with the continuous-spectrum lamp for controlling the amount of power delivered to the continuous-spectrum lamp. 
     
     
       11. The hybrid light source of  claim 10 , further comprising:
 two input terminals adapted to receive the phase-controlled voltage; 
 a first rectifier circuit coupled between the input terminals and generating a first rectified voltage at an output, the discrete-spectrum light source circuit coupled to the output of the first rectifier circuit for receiving the first rectified voltage. 
 
     
     
       12. The hybrid light source of  claim 11 , wherein the ballast circuit comprises a bus capacitor coupled across the output of the first rectifier circuit for producing a bus voltage, an inverter circuit for converting the bus voltage to a high-frequency AC voltage, and a resonant tank circuit for coupling the high-frequency AC voltage to the fluorescent lamp, the control circuit coupled to the inverter circuit for controlling the magnitude of a lamp current conducted through the fluorescent lamp. 
     
     
       13. The hybrid light source of  claim 11 , wherein the series combination of the semiconductor switch and the continuous-spectrum lamp of the continuous-spectrum light source circuit is coupled across the output of the first rectifier circuit for receiving the first rectified voltage. 
     
     
       14. The hybrid light source of  claim 11 , further comprising:
 a second rectifier circuit coupled between the input terminals and generating a second rectified voltage at an output, the series combination of the semiconductor switch and the continuous-spectrum lamp of the continuous-spectrum light source circuit coupled across the output of the second rectifier circuit for receiving the second rectified voltage. 
 
     
     
       15. The hybrid light source of  claim 10 , wherein the control circuit is operable to control the semiconductor switch of the continuous-spectrum light source circuit to pulse-width modulate the voltage provided across the continuous-spectrum lamp to control the amount of power delivered to the continuous-spectrum lamp when the magnitude of the phase-controlled voltage is above the predetermined zero-crossing threshold voltage. 
     
     
       16. The hybrid light source of  claim 1 , wherein the continuous-spectrum lamp comprises a halogen lamp and the continuous-spectrum light source drive circuit comprises a halogen drive circuit. 
     
     
       17. The hybrid light source of  claim 1 , wherein the zero-crossing threshold voltage of the zero-crossing detect circuit has a first magnitude when the phase-controlled voltage is less than the zero-crossing threshold voltage, and a second magnitude when the phase-controlled voltage is greater than the zero-crossing threshold voltage, the first magnitude greater than the second magnitude. 
     
     
       18. The hybrid light source of  claim 1 , wherein the control circuit turns off the discrete-spectrum lamp when the total light intensity is below the transition intensity, such that the continuous-spectrum lamp produces all of the total light intensity of the hybrid light source when the total light intensity is below the transition intensity. 
     
     
       19. A dimmable hybrid light source adapted to receive a phase-controlled voltage, the hybrid light source comprising:
 a discrete-spectrum light source circuit comprising a discrete-spectrum lamp; 
 a continuous-spectrum light source circuit comprising a continuous-spectrum lamp operable to conduct a continuous-spectrum lamp current; 
 a zero-crossing detect circuit for detecting when the magnitude of the phase-controlled voltage is approximately zero volts; and 
 a control circuit coupled to both the discrete-spectrum light source circuit and the continuous-spectrum light source circuit for individually controlling the amount of power delivered to each of the discrete-spectrum lamp and the continuous-spectrum lamp in response to the zero-crossing detect circuit; 
 wherein the control circuit controls the continuous-spectrum light source circuit such that the continuous-spectrum lamp is operable to conduct the continuous-spectrum lamp current when the phase-controlled voltage across the hybrid light source is approximately zero volts. 
 
     
     
       20. The hybrid light source of  claim 19 , wherein the continuous-spectrum light source circuit comprises at least one semiconductor switch coupled so as to control the flow of the continuous-spectrum lamp current through the continuous-spectrum lamp. 
     
     
       21. The hybrid light source of  claim 20 , further comprising:
 two input terminals adapted to receive the phase-controlled voltage; 
 a voltage doubler circuit coupled between the input terminals and generating a bus voltage at an output, the discrete-spectrum light source circuit coupled to the output of the voltage doubler circuit for receiving the bus voltage. 
 
     
     
       22. The hybrid light source of  claim 21 , wherein the discrete-spectrum lamp comprises a fluorescent lamp and the discrete-spectrum light source drive circuit comprises a ballast circuit for driving the fluorescent lamp, the ballast circuit comprising an inverter circuit for converting the bus voltage to a high-frequency AC voltage, and a resonant tank circuit for coupling the high-frequency AC voltage to the fluorescent lamp, the control circuit coupled to the inverter circuit for controlling the magnitude of a lamp current conducted through the fluorescent lamp. 
     
     
       23. The hybrid light source of  claim 21 , further comprising:
 a rectifier circuit coupled between the input terminals and generating a rectified voltage at an output, the series combination of the semiconductor switch and the continuous-spectrum lamp of the continuous-spectrum light source circuit coupled across the output of the rectifier circuit for receiving the second rectified voltage. 
 
     
     
       24. The hybrid light source of  claim 20 , wherein the control circuit controls the continuous-spectrum light source circuit to drive the semiconductor switch to be conductive and non-conductive with a duty cycle, the control circuit adjusting the duty cycle of the continuous-spectrum light source circuit to a maximum duty cycle such that the continuous-spectrum lamp conducts the continuous-spectrum lamp current when the magnitude of the phase-controlled voltage across the hybrid light source is approximately zero volts. 
     
     
       25. The hybrid light source of  claim 24 , wherein the continuous-spectrum lamp comprises a low-voltage halogen lamp and the continuous-spectrum light source drive circuit comprises a low-voltage halogen drive circuit and a low-voltage transformer. 
     
     
       26. The hybrid light source of  claim 19 , wherein the continuous-spectrum light source circuit comprises a semiconductor switch coupled in series electrical connection with the continuous-spectrum lamp for controlling the amount of power delivered to the continuous-spectrum lamp. 
     
     
       27. The hybrid light source of  claim 26 , further comprising:
 two input terminals adapted to receive the phase-controlled voltage; 
 a first rectifier circuit coupled between the input terminals and generating a first rectified voltage at an output, the discrete-spectrum light source circuit coupled to the output of the first rectifier circuit for receiving the first rectified voltage. 
 
     
     
       28. The hybrid light source of  claim 27 , wherein the discrete-spectrum lamp comprises a fluorescent lamp and the discrete-spectrum light source drive circuit comprises a ballast circuit for driving the fluorescent lamp, the ballast circuit comprising a bus capacitor coupled across the output of the first rectifier circuit for producing a bus voltage, and an inverter circuit for converting the bus voltage to a high-frequency AC voltage, and a resonant tank circuit for coupling the high-frequency AC voltage to the fluorescent lamp, the control circuit coupled to the inverter circuit for controlling the magnitude of a lamp current conducted through the fluorescent lamp. 
     
     
       29. The hybrid light source of  claim 27 , wherein the series combination of the semiconductor switch and the continuous-spectrum lamp of the continuous-spectrum light source circuit is coupled across the output of the first rectifier circuit for receiving the first rectified voltage. 
     
     
       30. The hybrid light source of  claim 27 , further comprising:
 a second rectifier circuit coupled between the input terminals and generating a second rectified voltage at an output, the series combination of the semiconductor switch and the continuous-spectrum lamp of the continuous-spectrum light source circuit coupled across the output of the second rectifier circuit for receiving the second rectified voltage. 
 
     
     
       31. The hybrid light source of  claim 19 , wherein the continuous-spectrum lamp comprises a halogen lamp and the continuous-spectrum light source drive circuit comprises a halogen drive circuit. 
     
     
       32. The hybrid light source of  claim 19 , wherein the zero-crossing threshold voltage of the zero-crossing detect circuit has a first magnitude when the phase-controlled voltage is less than the zero-crossing threshold voltage, and a second magnitude when the phase-controlled voltage is greater than the zero-crossing threshold voltage, the first magnitude greater than the second magnitude.